Structure and molecular dynamics of bis-1H-1,2,4-triazole succinic acid complex crystals

Abstract

Bis-1,2,4-triazole succinic acid (1H-1,2,4-triazole butanedioic acid (2 : 1)) belongs to the family of dicarboxylic acid compounds of nitrogen containing heterocyclic molecules which are expected to exhibit proton conductivity. We determined the crystal structure of the bis-1,2,4-triazole succinic acid complex by X-ray diffraction and compared it with that obtained by semi-empirical molecular orbital calculations. Wave-like layer structure with layers parallel to the (10) plane of the P2₁/c monoclinic space group was ascribed to the compound and we consider the structure to be formed as a result of a competition between strong specific interaction within a single layer and weak interlayer interactions of the N–H⋯π type hydrogen bond. The calculated distributions of the charge density as well as the electrostatic potential in the plane parallel to the triazole pentagon are in good agreement with those obtained from XRD data. The powder IR and Raman spectra of the title crystal and additionally of the 1H-1,2,4-triazole and β-succinic acid crystal were measured. The relation between these vibrational spectra and their relationship with the crystal structures are discussed. Particular attention is paid to the vibrations arising from the hydrogen bonds formed in these crystals.